This invention relates to a process for the retention of at least one substance dissolved in a solution; in particular, the process can involve the purification of industrial effluents by retaining toxic soluble substances, or the extraction of the precious metals from these effluents.
Numerous processes are known for the treatment of solutions in order to retain substances which they contain in the dissolved state. Some of these processes are based on the size of the substances in questionthese are, in particular, the techniques of ultrafiltration and reverse osmosis - and others are based on ion exchange. For example, Certificates of Addition Nos. 72/20,919 and 72/25,472 describe anion and cation exchange celluloses and their application to the treatment of certain types of industrial waste water: the substances dissolved in this waste water, and hence in the ionic state, are retained on the cellulose material by virtue of the ion exchange capacity which cellulose possesses.
The invention falls into the category which involves ion exchange, but its object is to overcome the disadvantages commonly encountered, namely clogging and limited capacity: clogging takes place because, unless the solutions treated are free of insoluble matter, the materials used clog up very rapidly, and limited capacity results in the escape of ions as soon as the ion exhange capacity is saturated by the substances dissolved in the solution.